Finn the Human and The Thunder King
by BattlexJester
Summary: Finn and Jake receive much needed help from and unexpected stranger. How will this newcomer effect our heroes and their world? What is there to know about him, and will they be ready for what looms over he horizon?
1. Chapter 1

Adventure Time fanfic (name pending)

Couple notes to start with:

Only saying this once: I don't own adventure time. Pendleton Ward still hasn't responded to my many generous offers to take at least 51% of adventure time off his hands. Besides the references to other stuff, the only things I own are the characters/other junk that weren't in the original show.

Another thing, this is a story I've been writing on and off for over a year, and it's the first thing outside school I've written. Please understand (lolz Nintendo reference), I'm sure more time went into coming up with ideas for this story than actually writing it, so forgive me if it seems a little scattered. Reviews and comments are always appreciated. I like to write, mostly to put my countless thoughts down on paper instead of daydreams in anatomy. If you guys and gals like my stuff, I may devote more time and explore the wide world that is fiction writing, so thanks in advance!

Any who, enough about me, on with the story!

This isn't necessarily an AU, it's just regular adventure time with non-canon events and characters (one being me ;D) Expect a few time skips and more dialogue than combat, but when there is combat, I'll try to make it as epic as possible. I'm still writing this thing, so if anybody has any cool ideas or suggestions fire away! I'm always open to ideas/criticism and I'll put credit where it's due. Jeez, way too much intro, anyways, let's get this party started!

-Chapter 1, New Challenger Approaching!-

Finn and Jake were trudging along the hilly grasslands of Ooo. They were just returning fom a dungeon crawl turned into a three day cave expedition. Needless to say, they were tired, hungry, weak, and in need of a shower. The cuts and scrapes on Finn, and Jakes' bruises and matted fur personified their spirits.

"Let's go in that mine, he says. It'll be fun he says." Jake grumbled to his brother.

"Shut it man, I'm too tired to deal with your sass right now. Plus, how was I supposed to know that scaffolding would collapse?" Finn groaned back to Jake.

"Finn, I'm pretty sure that sucky ladder was like, 80 percent termites."

"Yeah, I got a great look as we free fell down that shaft." Finn retorted sarcastically.

"Hehehe, shaft." Jake laughed to himself.

Finn gave Jake a confused look and didn't bother asking for an explanation. All of a sudden Finn's entire mood changed as he remembered his gathered loot.

"Hey! At least we still nabbed those raw power gems!" Finn reached for an absent backpack and his face returned to a frown, "…that are sitting in the middle of the spike trap where I got clipped in the shoulder." Finn lightly rubbed his aching shoulder while his hand was there. Jake stretched a hand up to his brother's head to pat it.

"Bro, I love you and all, but we have to have a talk about dungeon crawling."

-x-

After what seemed like an hour of walking, they came over another hill to see the treehouse off in the horizon. A smile came onto both of them as they started making plans what they'll do when they make it home.

"I'm going to make a stack of bacon pancakes ten feet high, take a very hot shower, and give Lady and the pups the biggest kiss ever…not in that order." Jake said thoughtfully.

"I should call Flame Princess and tell her what went down, I hope she didn't worry too much."

After another ten minutes of walking, the two heroes felt a faint rumbling in the dirt beneath them. They both stopped and started looking around the hilly landscape. Jake's ears were perked as he was trying to locate the source of said shakes.

"Bro, do you feel that?" Finn asked, trying to hide his apprehension.

"Awe, don't worry about it brother, it's probably just PB's herd of cotton candy horses."

Finn agreed and shrugged it off. As they walked the rumbling came back harder (that's what she said). Finn started to worry this may be more than some edible horses. Jake stopped and scrunched his nose in the air.

"*Sniff-Sniff*…Why do I smell pig?" Jake asked with obvious tension.

Suddenly the sound of a stampede roared behind them. Just before Finn could turn to react, he felt the dull side of a club slam into the back of his head. As Finn was falling to the ground, he saw Jake receive the same treatment.

-x-

Finn slowly opened his eyes. He was sprawled out on the ground, and his head was painfully throbbing. He looked to his right and could barely see Jake out cold and being tied up by their assailants. Finn felt the sharp prod of a blade poke his chest and snapped his gaze up to the cause of the threat. It was a masked goblin. He then noticed the rest of the posse, distorted sizes and shapes all riding giant animals, the giant tusks led him to believe they were boars. Finn was still very much dazed, so his senses haven't quite caught up yet. He could make out the goblin talking about "valuables" or something like that, but what he was saying was the least of his concerns right now.

'Oh stuff, this isn't good. Any day of the week Jake and I could mop the floor with these goons, but I don't have Jake's backup, and I'm barely conscious right now. What am I going to do? I didn't even get to call Flame Princess…' _Ask and ye shall receive. _

"YO! Do I have to separate you kids?!" A new voice rung out from the top of a bank not far from their position.

Every bandit Finn could see jerked and looked at the possible danger. Finn weakly turned his head to his left to get a look at the newcomer. All he could make out was a black and blue figure standing with his arms folded. The marauder who Finn guessed was the leader, rode out in front to shout, "Who are you weakling?!" He could hear the stranger snicker at the challenge.

"I don't think you and your boyfriends have room calling me a weakling as you beat up on an already beat up kid and his dog."

The leader became enraged as he spurred his boar to charge the silhouette with his axe raised. The figure chuckled and cupped his hands to yell, "So we're not going to talk about this like adults?!" The stranger's answer was another growl in spite. "Alrighty then, your funeral!" The newcomer taunted as he slid down the hill.

As he reached the bottom, Finn saw him pull a small rod from his back. "A stick?! He's gonna get cream-", Finn was left speechless after the next turn of events he witnessed. As if in slow motion, the rod grew at both ends, and contorted to what looked like the shape of a bow. At the snap of his fingers, a blue arc of electricity connected the tips of the now completed recurve bow.

The silhouette grabbed the middle of the arc, and as he pulled back, a solid bolt of lightning formed between his fingers, and let the "arrow" fly. The bolt through the air at a speed Finn had never seen before, so fast that the force alone knocked the bandit clean off the boar. A sudden explosion of electricity and light flashed and blasted the bandit skidding into the earth. The still-charging boar had no idea what it was getting in to.

"Alright Piglet, your turn!" The figure shouted as he started jogging towards his new foe. As if the whole bow out of nowhere thing wasn't enough, what happened next was just silly. Being closer than before, Finn could pick up a more detail. One detail being the bow glowing with blue runes before morphing again, this time straightening and lengthening (that's what she said). A blue spearhead formed on the end behind the stranger with small thunderbolt-shaped hooks flanking the blade.

Finn's new savior lowered into a dash, and as he neared he boar, he spun the spear blade out and slid with one knee down. Like the main dish at a luau, the spear staked the boar clean through. Still holding the spear with one hand, the newcomer stood up with surprising strength as he held the giant boar about his head. "Pulled pork anyone?" He said to the leaderless band of thieves.

The bandits looked from their crispy boss, then to his mount on a shish kebab, then down to the man responsible. Almost at once, they all let out a battle cry and charged forward to get revenge. "I'll take that as a no. Hey, catch!" The stranger said as he gripped the spear, swinging behind his back and throwing forward, launching the boar off his weapon. The huge animal collided with the front lines, knocking down most of their forces. "STEEERIIKE!" He said as he pumped a fist at his side.

The spear momentarily glowed with the same blue runes, and molded back into its first rod form as the figure slid it behind him again. He cracked his knuckles and said, "Alright you dweebs, let's get to know each other." He then dashed towards the bandit posse still standing. Finn lost sight of him as he dove into the fray of the bandits. All Finn could muster was, "Whoah…awesome." Just before he slipped into the black void again.

-x-

WOW that was a long first chapter. Thanks for sticking around those who didn't rage quit halfway through. I'm still learning my way around the site profile wise, so don't before afraid to make fun of me if I label or name something wrong, help is always awesome. No idea when I'll get the next chapter up or how long I should make them, that could be totally up to you all. Like I said, any constructive criticism is always awesome, and I hope you guys enjoyed it!


	2. Chapter 2

Hey guys, back for round two! First off, s/o to the first follower of the story, adventureNowAndThen. Meant a lot to get a response that quick. Anyways, something I may have mentioned last time, I have only a part of this written already, so hopefully I can space out what I have already to make it easy to read and keep up on updates while writing and such. I lied when I said I'll only say it once, I'll say it often so I don't get my arse fined. **Disclaimer:** I don't own Adventure Time, at all, period.

-x-

-Chapter 2, A familiar face (structure)-

Finn felt the familiar warmth of his bed, oh how he missed that poorly-put-together bed. The small pile of animal hides provided more comfort than a fireplace.

'Oh my Glob, I never thought I'd love my bed this much.' Finn smiled inwardly, enjoying his newfound nap-vana. 'I'm so glad we made it back from that dumb cave. I really need to give FP a call when I get up…man, IF I get up. A few more minutes can't hurt though.' He nodded as he repositioned himself.

'Wait…how the heck did I get here?' Finn opened to see his nightstand, and the window beside it letting in nothing but moonlight, thankfully his lamp was on. Finn slowly sat up, feeling his head throbbing like before, leading him to groan softly in discomfort. "Oh stuff, my head is killing me." He reached for said head and felt tightly wrapped bandages around a stiff knot on the back of his noggin. 'Huh? Did Jake do this?'

"That should about do it!" a familiar voice said from Jake's side of the room. Finn looked and saw their savior form before, the colors of his clothes and his voice let the memories start flowing back into his concussed cranium. Finn saw him wrapping similar bandages around Jake's head.

"Finn! You're awake!" Jake happily cheered. The stranger turned to look at Finn, his face mostly covered by the shadow of a thick black hood. All Finn could make out was the bottom of a deep scar and some 5 o'clock shadow.

"Well rise and shine nap-time princess!" The man said chuckling. He threw the rest of the gauze into an open backpack sitting next to him. "Luckily you guys didn't bleed a whole lot, I'm surprised both of your skulls weren't cracked, you both heal fast. Still, don't do anything too cray for at least a week, gotta make sure y'all don't get poo brain. I'll check again in a little bit to make sure the bandages hold, then I'll be out of your hair." He said looking out Finn's window.

"How do you know so much about medicine and stuff?" Jake asked rubbing his head

"I learned some basics back home, but when you travel as much as I do, you pick up a few things." He said with a sincere smile.

"What happened back there?" Finn inquired while trying to get a look under his hood.

"You two goons were ambushed by the notorious Boar Bandits, from what I heard they were after your little treasure trove downstairs, you may want to find a different place for that by the way, I could literally see that from outside." Finn wasn't really sure how react to being teased by a complete stranger. "Speaking of treasure, I wonder what kind of bounty I can get by turning in their leader…" the stranger said while holding his chin.

"You beat all those guys by yourself?!" Finn focused on the more important issue as he remembered just before he passed out.

"Oh man! You should have seen it Finn!" Jake decided to join in. "That magic glowy stick doohickey is a work of art with the changing thing it did, plus he beat down all those jerks and their rides with his BARE HANDS!" Jake exclaimed with big hand gestures. "I've never seen someone tear through bad guys so fast." Finn looked at the stranger with wonder.

"Shoot guys, it was nothing, really." He said while scratching the back of his hood trying to hide a bit of embarrassment.

"I woke up right as he started going ape of those bandits, I wanted to help, but they had me tied up with some kind of magic rope. He cut me loose after he was done and helped me walk and carried you back here. Jake explained to his brother.

"Th- thanks man!" Finn gratefully said while trying to process everything.

"Don't mention it! I was just passing by, and no way I wouldn't help some fellow heroes out." He said with a toothy.

"Oh yeah!" Finn can't believe he hasn't introduced them yet. "I'm Finn, and this is my brother best friend Jake." Jake made a small wave, while smiling.

"Cool! I'm- oh wait, forgot I had my hood still on." He pulled his hood down and ruffled out his short, messy hair. "My name's Spencer!" He said with a toothy grin.

Finn almost didn't believe what he saw. He saw a head of hair like he had. He saw two eyes like he had. He saw a nose and mouth like he had. He saw peachy skin like his. He saw a human before him, like he was.

-x-

In an instant, Finn was able to take in everything about him. He had shorter dark brown hair that was messier towards the front. Some thick stubble went across his face to connect his unruly hair. The most striking features about him were his near-glowing steel blue eyes, and a deep scar of a single line started above his left eye and ended under his right ear. Finn wouldn't say this out loud, but he had a big head and jaw to match his body. This dude was big. He was easily a head, if not a head and a half taller than Finn. He had a barrel-chest and broad shoulders that narrowed in a V-shape to his wait, witch split off into equally big legs, and no homo, this dude was pretty ripped. Finn definitely didn't want to try fighting this guy, not yet anyway. His gear confused him, he wasn't wearing armor, albeit pieces of it. The most prominent was a blue-colored steel shoulder guard with a spike on his right arm, and a smaller guard with no spike on the left. Each had their own leather strap holding them on, the spike guard's strap being thicker and holding a couple vials and a pouch while the left held a small metal plate over the heart area. Finn guessed the bigger strap helped hold his backpack on. There was black wrapping around both elbows and metal-plated black finger-less gloves. Moving down, Spencer wore a utility belt with a butt load of pouches along the sides, and a blue thunderbolt buckle, huh, appropriate. All that was left was a hip pouch on his left side and black combats boots. Under all his gear Spencer wore a sleeveless black muscle shirt and loose blue jeans with black patches on the knees.

"You…you're human?" Finn barely chocked out.

"Um, yeah? Why is that weird to be?" Spencer asked with honest confusion.

"We haven't seen any real humans besides a super old guy down in the MO factory." Jake explained to their guest.

"What?!" Spencer chocked on a water bottle he pulled out of his backpack. "There was at least five human villages last time I was here, plus there's all kinds of humans where I'm from! I live in a temple with a bunch, plus there's a few villages around there too… I can't believe things have changed so much here." Spencer said looking at the floor.

"There's THAT many humans there?!" Finn would jump out of bed if not for the headache. "Can I go there?!" Finn saw this as his chance to truly connect with his people and maybe find something out about his past.

"…here's the thing…" Spencer started sheepishly. "I'd take you there in a heartbeat, don't get me wrong, but my boat crashed into the rocky shore on my way here. I'll have to build a whole 'nother boat to get back home. I'm pretty sure it's uncharted waters as far as Ooo is concerned." Spencer finished giving Finn an apologetic look.

"So, if you're not from Ooo, what else is there? I don't know much about anywhere else." Jake rolled on to his stomach after listening to Spencer's story about home. Spencer walked over and sat at the foot of Finn's bed. Finn and Jake got comfortable in anticipation of a story.

Spencer starting wringing his hands and took on a thoughtful look as he was getting ready to describe his home. "Well, I live on an island south the shores of here. It's summer all year long, and that's pretty awesome…"

-x-

BOOM, how was that for a somewhat mind bomb? Seriously though, thanks for everyone giving my little old story another go. Let me know if you want the chapters longer or shorter, and when you want me to update. Till next time!


	3. Chapter 3

Hey guys and gals! Sorry for that long wait, second semester is becoming a real biatch. I'll try to be more punctual now that we're getting into the mid-semester grind. You may or may not have noticed I changed the rating, don't worry, this isn't going to turn into a blood and guts filled sexcapade. I just wanted to be safe in case something gets slipped in there may be a wee too intense for a teenager audience. Anyways, on with the story!

-x-

-Chapter 3, Stories of Home-

"I'm from an island a few miles south the shores here. I live in monastery with some monks, and there's a lot of really nice towns spread out all over the place. Like I said, summer all year, which is pretty freaking awesome." Spencer finished his description of home. After using wide motion with both hands, he sat back on his elbows on the foot of Finn's bed.

Finn was intrigued by the unknown land, and thought about all the adventures he could have there. Jake "ooh-d and ah-d" at the summer part.

"Summer would be awful nice year-round." Jake huffed as he thought about winter and those stupid knife storms that roll in during the spring. Spencer sighed and reminisced as he continued.

"Yeah, I owe everything to those monks. They raised me ever since Mom died and Dad skipped out. They can be pretty uptight, but they're really cool people! They taught me everything I know: medicine, smithing, enchanting, most what I know about fighting,-"

"Hold up!" Finn interjected with a shocked expression. Spencer looked back at his fellow human curiously. "What do a bunch of monks know about fighting like that, or any of that stuff you do?!"

"I'm glad you asked!" Spencer chuckled and got up as he pulled over a chair so he could see both Finn and Jake. He leaned back in the chair with his hands behind his head. "These peeps aren't your run-of-the-mill, pray-all-day, pacifist dudes…Ever heard of the War Monks?" Spencer finished with a grin.

"No, but they sound awesome…" Finn thoughtfully scratched his chin.

"No way!" Jake exclaimed after pondering that familiar title. "I know who they are! Dad used to tell me all kinds of stories from before the Rainicorn-Dog Wars! But, didn't they all disband after the Shogun Era?"

"Color me impressed, Jake! I didn't think they still put that stuff in the books." Spencer chuckled at Jake's response.

"Hey, I may not be the ripest apple in the tree, but history was my fave subject." Jake felt pretty good being ahead of the game.

Finn looked back and forth between Jake and Spencer with a very puzzled look on his face. "Can someone please tell me about this samurai-battle-monk jazz now?!" Finn felt pretty stupid being left out. Spencer thoughtfully clicked his tongue and looked from Finn to Jake and said,

"Jake, you want to take this one? It may make more sense coming from a friend." Spencer said as he leaned forward in the chair as he rummaged through his bag.

"It would be my pleasure milord." Jake sarcastically bowed his head. Spencer scoffed as he wiped his face and neck with a rag he wetted with his bottle.

"It was like this, bro…" Jake moved to sit against the wall with his pillow behind his still-sore head. "A way super long time ago, Ooo was ruled by shoguns and their samurais and all that." Finn pulled his knees close as Jake continued.

"All the land was split up between three lords. They acted as one governing body so no one could go totes power-hungry, and the only reason they never fought with each other was the War Monks. They were the high scholars AND divine peacekeepers of Ooo. Obviously, they were super smart and crazy strong."

"Whoa…" Finn simply replied in wonder. He was shocked people like monks could have such power and authority. "If they were so cool, then why did the band break up?" Finn asked his brother.

"I'm getting to that Mr. Impatient!" Jake huffed. Finn rolled his eyes at his always-dramatic brother. "One day, the lords got together and decided they would overthrow the monks so they would have absolute power over Ooo. It took a long time, but eventually the monks lost to sheer numbers. What I don't know is how the temple you came from survived, Spencer. More importantly, what are the monks doing on an island THAT far out?" A puzzled Jake looked over at his house guest.

"I can answer both questions with one epic story!" Spencer said with a grin and one finger held up. "Just like Jake said, our monasteries were being sacked one by one. The parish I'm from was on the end of a long peninsula not far south of here. Near the end of the conflict, the lords and the remainder of the three armies showed up at our doorstep. The three butt-lords themselves rode up front to talk with Gregor the Great, the arch-monk at that time, who was by himself in front of the monastery. They gave Gregor and the rest of the monks their ultimatum: surrender and live as the Lords' personal strike force, or resist and forever be forgotten."

"What'd they do?!" Finn asked with growing anticipation.

"The really cool part." Spencer said with a wink. "Gregor said they wish to simply leave in peace, and leave the lords to fight amongst themselves. They laughed at his face and asked how they were going to get past their combined armies. He just smiled, reared back, and kicked the ground so hard the entire width of the peninsula cracked, essentially separating the peninsula from the mainland. Then he dug his hands in the earth and kicked away, scooting the new island quite a ways away. Just as the lords signaled and archery attack, a huge ice wall rose up between the mainland and our island to protect it. On top of it was Gregor's wife, Maria the Mighty." Spencer continued.

"Then Maria tidal-waved the lords and a big portion of the army away and froze them where they stood. Those goons could just watch as she carried the island away with the tide. They called to lords as they drifted away and said, as long as you don't disturb us, you'll never see us again. The island thrived from all the good resources, some people left the mainland to colonize our new island, and the monks continued their way of life and whatnot. The end." Spencer finished with a sigh and light smile.

-x-

I know this may seem like a weird place to end it, but I didn't want this big old backstory split between chapters. We'll find out the behind the scenes stuff next chapter. I'll try to beef up later chapters, I realize the first two chapters weren't as long compared to other stories here, contrary to what I first thought. Thanks for sticking around! Reviews would be like early Christmas, don't forget those always help. Until next time!


End file.
